This invention relates generally to the field of minimally invasive surgery, such as intervertebral disc and cataract surgery and more particularly to a handpiece for practicing the liquefraction technique.
The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of the lens onto the retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and lens.
When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL).
In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, a thin phacoemulsification cutting tip is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquifies or emulsifies the lens so that the lens may be aspirated out of the eye. The diseased lens, once removed, is replaced by an artificial lens.
Recently, a new tissue removal technique has been developed that involves the injection of hot (approximately 45° C. to 105° C.) water or saline to liquefy or gellate tissue, such as the hard lens nucleus, thereby making it possible to aspirate the liquefied tissue. Aspiration is conducted with the injection of the heated solution and the injection of a relatively cool solution, thereby quickly cooling and removing the heated solution. One application of this technique is more fully described in U.S. Pat. No. 5,616,120 (Andrew, et al.), the entire contents of which is incorporated herein by reference. The apparatus disclosed in the publication, however, heats the solution separately from the surgical handpiece. Temperature control of the heated solution can be difficult because the fluid tubings feeding the handpiece typically are up to two meters long, and the heated solution can cool considerably as it travels down the length of the tubing.
The use of electrosurgical handpieces to remove tissue is known. For example, U.S. Pat. No. 5,009,656 (Reimels), the entire contents of which is incorporated herein by reference, describes an electrosurgical handpiece having an inner and an outer tube separated by an insulator. Current is passed between the inner and the outer tube to cause a spark that is used to cut tissue. This device intentionally creates an air gap between the electrodes to facilitate sparking, and does not use heated fluid as the cutting medium.
In addition, U.S. Pat. No. 6,156,036 (Sussman, et al.), the entire contents of which, and particularly the material at column 2, lines 40-67, column 3, lines 1-67 and column 4, lines 1-27, being incorporated herein by reference, discloses a surgical handpiece having a tip with at least two coaxially spaced electrically conductive tubes. The tubes are separated by an electrical insulator. The interior of the inner tube is used for aspiration of liquefied tissue. The distal portion of the interior tube terminates just inside of the outer tube so as to form a boiling region. Electrical current is passed between the inner and outer tube to rapidly boil any surgical fluid in the boiling region. The boiling fluid rapidly expands out of the ring between the tube ends and forces hot fluid to contact the targeted tissue, thereby liquefying the tissue and allowing the tissue to be aspirated. This reference, however, does not describe a tip having a source of irrigation fluid. Fluid must enter the boiling region through the aspiration opening. The aspiration opening is occluding by the material being ablated, the boiling chamber may not fill with surgical fluid.
Therefore, a need continues to exist for a surgical handpiece that can heat internally the solution and create high pressure, high rise rate waves or pulses used to perform the liquefraction technique and that contains a pathway for surgical fluid to enter the boiling chamber even if the aspiration opening is occluded.